JUNE, 1906. Netw Forms or CoNcRETIONS—NICHOLS. 4I 
It was the opinion of James D. Dana* that these two banks were, 
in comparatively recent historical times, islands, which were even 
mapped as “The False Bermudas.”’ Early accounts of these banks 
described them as “‘rocky ledges.’’} The ship Challenger visited the 
bank of that name upon the 23d of April, 1873. Upon its map of the 
region} the character of the bank is given as coral. Sir C. Wyville 
Thompson,§ who was with the Challenger expedition, says: ‘‘The 
bank, which seems to be about five miles across, consists mainly of 
large rounded pebbles of the substance of the Bermuda serpuline reef. 
There is an abundant growth all over the pebbles of the pretty little 
branching corals, Madracts asperula and M. hellana,”” He mentions 
also that starfish and other animals were brought up in the dredge. 
Mr. Bean, dredging in 28 fathoms, found that the bottom was 
covered with the nodules under consideration, which are doubtless 
identical with Sir Wyville Thompson’s pebbles: The nodules were, 
however, imbedded in calcareous ooze, and although covered by 
-living forms, the branching skeletons, which may well correspond 
with Madracts, appear from inspection of the dried specimens to 
have been dead sufficiently long to become encrusted with bryozoa 
and nullipora. 
If these nodules are rolled fragments of serpuline limestone, both 
the existence within a few hundred years of the False Bermudas and 
their extremely rapid subsidence is as good as proven. The three 
and one half miles of deep sea which separate the banks from the 
nearest reefs offer an insuperable obstacle to the transportation of 
pebbles in such large numbers. Such nodules of fragmental origin 
also could not form im situ under present conditions, for wave action 
at depths of twenty-four to thirty fathoms is either very weak or 
entirely lacking. The current of three knots has not sufficient 
power to round boulders of such size. If, however, they are 
accretions, they have little or no apparent bearing upon these ques- 
tions, and the interest in them arises from other sources. 
The nodules from the Challenger bank (Plate XXV) in the 
possession of the Museum were dredged, as already stated, from a 
depth of about twenty-eight fathoms. The nodules are roughly 
spherical, with pitted and irregular surfaces. When collected, they 
were covered with living hydrozoa, other animal forms and algae. The 
*Corals and Coral Islands, p. 187. 
tIbid. 
fChallenger Report: Narrative: Vol. I, facing p. 140. 
§Voyage of the Challenger: The Atlantic, Vol. I, p. 333. 
